Technical Field
The present invention relates to a rotor for a rotating electric machine that is mounted in a vehicle, such as a hybrid car or an electric car, and used as an electric motor or a power generator.
Related Art
Conventionally, a rotating-field type synchronous motor (referred to, hereinafter, as an interior permanent magnet [IPM] motor) is known as a rotating electric machine that is mounted and used in a vehicle. The IPM motor has a structure in which a magnet is embedded within a rotor. The IPM motor is capable of using both reluctance torque generated by magnetization of the rotor and torque generated by magnetization of the magnet. Because of its high efficiency, the IPM motor is favorably used in hybrid cars, electric cars, and the like.
The IPM motor includes a stator and a rotor. The stator and the rotor are disposed such as to oppose each other in a radial direction. A rotor that includes a rotor core and a plurality of magnets is known. In the rotor, the rotor core is disposed such as to oppose the stator in the radial direction. The rotor core has a plurality of magnet housing holes that are arrayed in a circumferential direction. Each of the plurality of magnets is housed in a magnet housing hole. The plurality of magnets form a plurality of magnetic poles that are arrayed in the circumferential direction.
JP-A-2011-101504 discloses a rotor core that has a flux barrier (magnetic gap) and a bridge portion. The flux bather is formed between a q-axis core portion and a magnet. The q-axis core portion is formed between magnetic poles that are adjacent to each other in the circumferential direction of the rotor. The bridge portion is formed between a stator-side core portion and the q-axis core portion. The stator-side core portion is positioned on the stator side of the magnet.
In this instance, the width of the bridge portion in the radial direction increases from the magnet side towards the q-axis core portion side in the end portion on the q-axis core portion side. As a result, concentration of stress occurring in the bridge portion based on centrifugal force during rotation of the rotor can be dispersed.
In the above-described conventional rotor, the magnets embedded in the rotor core are fixed and held by a filler material. The filler material is composed of a non-magnetic material, such as resin, and fills the area between the magnet and the wall surface of the magnet housing hole. The flux bather is continuously and integrally formed with the magnet housing hole on the q-axis core portion side of the magnet housing hole.
The flux barrier may also be filled with the filler material that fixes and holds the magnet. When the flux barrier is also filled with the filler material, the filler material repeatedly expands and contracts in accompaniment with the change in environmental temperature during operation and stop of the rotating electric machine. At this time, concentration of stress easily occurs in the bridge portion of the rotor core. JP-A-2011-101504 does not include any disclosure regarding the concentration of stress occurring in the bridge portion in accompaniment with the temperature change in the filler material that fills the flux barrier.